netdev - Re: [PATCH net] ip6_tunnel: fix GRE6 segmentation

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Message-ID: <20210624093305.4b4bb49e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 24 Jun 2021 09:33:05 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Ahern <dsahern@...il.com>
Cc:     Guillaume Nault <gnault@...hat.com>, davem@...emloft.net,
        netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org,
        dsahern@...nel.org, vfedorenko@...ek.ru
Subject: Re: [PATCH net] ip6_tunnel: fix GRE6 segmentation

On Thu, 24 Jun 2021 08:36:12 -0600 David Ahern wrote:
> >> It is to let IPv6 DAD to complete otherwise the address will not be
> >> selected as a source address. That typically results in test failures.
> >> There are sysctl settings that can prevent the race and hence the need
> >> for the sleep.  
> > 
> > But Jakub's script uses "nodad" in the "ip address add ..." commands.
> > Isn't that supposed to disable DAD entirely for the new address?
> > Why would it need an additional "sleep 2"?
> >   
> 
> it should yes. I think the selftests have acquired a blend of nodad,
> sysctl and sleep. I'm sure it could be cleaned up and made consistent.

I was guessing that the DAD is happening on the link local address,
that's why, no? I'm using link local in the underlay.